yesterday i had to turn off the power supply to get the radio running; is this normal;

I wouldn’t call it “normal”, but it is not unusual. You don’t say what radio and software version you have, so cannot make specific comments.

about once or twice a month my 6600M will need a power off because either the radio or display software got confused - it happens. I have to say it occurs mostly when I transmit with too high power into my auto-tuner. Probably RF in the shack confuses some of the electronics.

as to ATU, it is a bunch of relays, so yes it will “click”. I don’t use mine, always set it to bypass because I use an auto tuner at the antenna feed point.